An interferometer is an apparatus that shows interference between two or more wave trains coming from the same source and that compares wavelengths with measurable displacements of reflection. A interferometer antennae array has many applications. For example, it can be used to determine the aximuth of a distant electromagnetic source by comparing the signal phases at the output terminals of two or more antennae receiving a common signal from that source.
Previous interferometer antennae have used a flat plate array. There are two common types of flat plate arrays. One uses a single array assembly and the other, discrete elements. The latter type of flat plate array consists of a heavy structure with accurately spaced cylindrical holes. The holes are lined with metal rings length of the structure and rings, respectively, are of a specified multiple fraction of a wavelength. This assemblage is placed on a ground plane which has apertures, corresponding to the cylindrical holes for the electrical connections, e.g. connectors and cables.
The interferometer antennae which has a flat plate array that utilizes discrete elements can be suitably mounted on any flat or planar surface. The problem with this type of array is that it can not conform to a nonplanar surface. Shaping this array around a nonplanar surface misaligns the holes by distorting the required spacing between them. Also, the rotational alignment between paired antennae is thrown off. For a flat plate array utilizing discrete elements, rotational alignment between paired antennae is accomplished by rotating each spiral antennae until they are "clocked" electrically, aligining the signal phases. So even if the mounting structure is first conformed to a nonplanar surface, the difficulty of aligning paired antennae is compounded.
Accordingly, the principal object of the present invention is to enable an interferometer antennae array to be conformally shaped to a nonplanar surface, e.g. a cylindrical surface, while maintaining precise mechanical alignment between spiral antennae. Other objects of the invention are to eliminate the cavities formed by the metal rings, to decrease the weight of the groundplane while maintaining its structural rigidity and mechanical alignment, and to simplify the electrical connections.